Kev Greenwood Posted January 18, 2013 Share Posted January 18, 2013 just bought a Slipstream 74inch MXS, got a Turnigy 50-65 270kv motor on the front fitted a 19-10 prop but only getting 880Watts, i want around 16-1800 watts, anyone got any ideas on what size prop 2 or 3 blade i would need to get this amount of power, apparently motor is capable of 2000W on 6S.... cheers Kev Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted January 18, 2013 Share Posted January 18, 2013 Well, sadly as you know there is no simple formula. As a rule of thumb diameter tends to "put it on" more than pitch - so if you don't have ground clearance problems you could look at 20x11 - That would certainly up the power - whether it would be enough is a different matter and the trouble is that at these sizes "sucking and seeing" is getting a bit expensive! BEB PS I assume your ESC can handle getting on for 100 amps? Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted January 18, 2013 Share Posted January 18, 2013 Hi Kev, this is the spec of the 5065: Model: SK50-65 270 Kv: 270rpm/v Turns: 8 Resistance: 38m-Ohm Idle Current: 0.7 Shaft: 8mm Weight: 434g Rated Power: 2100W ESC: 80A Cell count: 6-8S Suggested Prop: (20~22inch) Tested props: 20x8@ 32amp on 6S 21X8 @ 43amp on 6S 22X12 @ 66amp on 6S On 6s 24.6V you will need to draw around 73A to get 1800 Watts which needs something even bigger than a 22 x 12 and you will probably get more like 22.2V on load so you will need 80A On 8s 32.8V you will need 55A to get 1800 Watts, so around a 22x10 I flew my Spitfire on a 5065 270 with 8S and a 20 x 14 three blader and got around 1800-2000W So yes the motor will produce 2kw but on 6S you will probably exceed the current rating. I popped a 110A esc on the Spitfire during the first few spool ups. I suggest the same prop on 8S and see what you get? Cheers Danny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted January 18, 2013 Share Posted January 18, 2013 oops BEB beat me to it, let me emphasise my numbers are ball park, and different cells may hold their voltages better than others under this sort of load. so as BEB says a bit of suck it and see. The 5065 is an excellent motor though, I have several, including some with slightly higher kv's. Is yours the black xp or the gold aerodrive version? Edited By Danny Fenton on 18/01/2013 22:11:52 Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted January 18, 2013 Share Posted January 18, 2013 Hi Danny and BEB. On behalf of Kev ,a mate and ex student of mine ,thanks for the great replies .He got the motor from me and I am trying to encourage him to look up motor specs and figure out what they all mean in practical terms . Kev is running the motor with a 200A ! ESC so no probs there then.BTW Danny the motor is the Gold one . Tom. Oh thought Kev had gone to bed ,but he has just come up in the friends box. . Edited By Tom Wright 2 on 18/01/2013 22:33:29 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted January 18, 2013 Share Posted January 18, 2013 Ahh okay Tom, the motor I used in the Spitfire was the gold aerodrive 270kV I am not sure I would push them too hard, I fly scale so the motor is on low power most of the time only ocassionally pushed hard. The model its going in sounds like it may push it hard for more of the duty cycle if you know what I mean lol I still think upping the cell count to 8, and try that 19 x 10 with a wattmeter Good luck D Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted January 18, 2013 Share Posted January 18, 2013 Yea to right Danny ,I already suggested Kev runs the motor well within specs , I always do that with mine and never have problems . Kev were are you ? in the shed freezing to death again . Tom. Quote Link to comment Share on other sites More sharing options...
Kev Greenwood Posted January 18, 2013 Author Share Posted January 18, 2013 Hi Tom im in the house now lol.....like i mentioned in the email to you, i dont really want to go over 6S as my charger will only go that far, i know i can put two 4S batts together, but i would need lots of 4S batts. If i can run the motor near to its max, and not over do it, that would be fine with me, i dont want the plane to be super quick, just lots for reserve power for climbout from prop hanging/slow flying. I was looking at a thread on the interweb about a guy with the same plane with a 6S setup and he was getting around 1200W but complained about he couldnt climb vertical out of a prop hang stunt. I know im not at that stage yet, but i can try high up.......my extra 330s is pulling just under a 1000w and that wont climb out of a prop hang. i will try Gliders and see if i can go to a 19inch 3 blade and a 22 2 blade and see what i get then. If i can get 1500-1600w without over cooking the motor, that would be great. Kev my modified motor mount with Toms supplied motor. Edited By Kev Greenwood on 18/01/2013 23:11:59 Edited By Kev Greenwood on 18/01/2013 23:12:57 Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted January 18, 2013 Share Posted January 18, 2013 Kev . As BEB suggested the pursuit of power can get expensive , low KV motors can be propped up in larger increments than high KV so the motor specs tell you that a 22x12 prop will draw 66A and return around 1580 W .. Hope that helps,and the motor does better than the 50-60 that lasted all of 20 secs . Tom. Edited By Tom Wright 2 on 18/01/2013 23:22:54 Quote Link to comment Share on other sites More sharing options...
Kev Greenwood Posted January 18, 2013 Author Share Posted January 18, 2013 that sounds good to me Tom, just ordered a 22x12 and a 20x12 prop from giant shark so will give it a go with those, if that pulls 1580W on the 22x12 would a 21x? or a 20x? 3 blade give the same power? i will have to measure 22 inch on the front of the plane. Quote Link to comment Share on other sites More sharing options...
Kev Greenwood Posted January 18, 2013 Author Share Posted January 18, 2013 Posted by Tom Wright 2 on 18/01/2013 23:18:45 Hope that helps,and the motor does better than the 50-60 that lasted all of 20 secs . Tom. yea im sure it will Tom, ive sent Hobbyking the pics and an explanation of the problem and details of my setup......lets see it they refund the money!!!! Kev Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted January 18, 2013 Share Posted January 18, 2013 Kev . Again as previously suggested it's a suck it and see situation .Therorcticaly three blades are less efficient ,and note that the power drawn from the lipo is not necessarily an indication that the prop is producing more power as it depends on he prop efficiency and how well its matched to the motor. Just make sure you wear a suit of armour when running up those beasts in the workshop . Tom. Quote Link to comment Share on other sites More sharing options...
Kev Greenwood Posted January 18, 2013 Author Share Posted January 18, 2013 Im just worried about the prop clearance Tom.......but yea i will make sure im well out of the way when they spin up.....lol oh by the way, i managed to get a new cowl for that spitfire i got from Pete £16 with postage..... Kev Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted January 18, 2013 Share Posted January 18, 2013 As a very rough estimate Kev, in the ic world anyway, a 3 blade will behave similar to a 2 blade one inch bigger diameter, and you leave the pitch alone. So if you have a 20x10 two blade - you'd try a 19x10 three blade. BUT. Some things to keep in mind; 1. This is an IC engine based "rule" 2. It very approximate! 3. I can vouch for the fact that with IC and prop sizes up to about 14" diameter it works OK - but beyond that I don't know. Props get more efficient as they get bigger and tip velocities increase. So bigger props can be operating under very different conditions. As most folks have said - you have to suck it see I'm afraid. BEB Quote Link to comment Share on other sites More sharing options...
Matt How Posted October 3, 2013 Share Posted October 3, 2013 Hi alL I am converting a yt international p38 to electric. Got motors esc etc sorted. But here is my dilemma, I require a 16x8 triple blades props that contra rotate. Does anyone make these? Where can I get them from? Heeeeellllllp kind regards matt Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted October 3, 2013 Share Posted October 3, 2013 Hi Matt, I am not sure what KV rating you are running but if you keep the revs down then the Varioprop from Christian Ramoser would be my weapon of choice. But I would be on a much higher pitch than you are. An 8 inch pitch is for high reving ic engines. My chipmunk flies on a 15 x 10 for example. The Varioprops are only rated to around 7k rpm dependent on the particular prop. Cheers Danny Quote Link to comment Share on other sites More sharing options...
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